1. Field of the Invention
The present disclosure relates to an image processing device, an image processing method, an image processing program, and an imaging system that correct color deviation in a multiband image captured using a frame sequential method.
2. Description of the Related Art
As a method of generating a color image, a method of combining a plurality of images (multiband images) acquired by capturing images in respective wavelength bands is known.
As a method of capturing the multiband images, a frame sequential method is known. The frame sequential method is a method of capturing images in such a manner that a filter wheel in which a plurality of bandpass filters is arranged is disposed in front of a camera, and the filter wheel is rotated, whereby the images are sequentially captured through the respective bandpass filters.
Meanwhile, chromatic aberration typically occurs in a lens due to different focal positions that depend on colors of beams of light that pass through the lens. This is caused by the fact that a refractive index of a substance varies in accordance with a wavelength of light. More specifically, a phenomenon occurs, that is, a position of an image surface is displaced in a front-back direction on an optical axis in accordance with the wavelength band, or the size of an image varies. For example, assuming that a position of a green image surface is a reference, an image of blue having a shorter wavelength than green is formed on a side close to the lens, and an image of red having a longer wavelength than green is formed on a side far from the lens. Therefore, in a case where the above-mentioned multiband images are combined to generate the color image, images of the same object are displaced in accordance with the colors, that is, so-called color deviation occurs.
In order to solve such a problem, for example, JP 2000-299874 A discloses a technique for correcting the color deviation. Specifically, an edge in an image is extracted by means of the Laplacian operation that performs a second order differential, and a chromatic aberration amount of each color component is calculated based on the edge. Furthermore, a position adjustment is performed between images of the different color components based on a chromatic aberration characteristic curve calculated from the chromatic aberration amount, whereby the color deviation is corrected.
JP 2008-244833 A also discloses a technique for correcting the color deviation. Specifically, a correction table in which pieces of chromatic aberration characteristic data for respective wavelength bands are stored is prepared in advance, and a position adjustment between images in the respective wavelength bands, that is, spectral images, is performed based on the pieces of chromatic aberration characteristic data read from the correction table, whereby the color deviation is corrected.